Physiological, anatomical, biochemical, and cytogenetic effects of thiamethoxam treatment on Allium cepa (amaryllidaceae) L.

In the present study, toxic effects of active substance thiamethoxam of the insecticide Eforia were investigated on Allium cepa L. For this aim, we used the germination percentage, root length, weight gain, malondialdehyde (MDA) level, frequency of micronucleus (MN), chromosomal aberrations (CAs), and mitotic index (MI) as indicators of toxicity. Also, the changes in the root anatomy of A. cepa seeds treated with thiamethoxam were examined. The seeds in all the treatment groups were treated with three different doses (100, 250, and 500 mg/kg) of thiamethoxam for 72 h. The results showed that there were significant alterations in the germination percentage, root length, weight gain, MDA level, MN, CAs, and MI frequency depending on application dose in the seeds exposed to thiamethoxam compared to control group. Thiamethoxam treatments significantly reduced the germination percentage, root length, and weight gain in all the treatment groups (P < 0.05). But, it caused an increase in MN and CAs formation (P < 0.05). It was also found that thiamethoxam has a mito-depressive action on mitosis, and the MI was decreased depending on the dose of applied-thiamethoxam (P < 0.05). About 100, 250, and 500 mg/kg doses of thiamethoxam significantly enhanced the lipid peroxidation and caused an increase in MDA levels at each dose treatment (P < 0.05). Some anatomical damages such as necrotic cell death, unclear vascular tissue, unclear epidermis layer, cell deformation, and unusual form of cell nucleus were observed by using light micrographs. Each dose of thiamethoxam caused severe toxic effects on A. cepa cells, and the maximum toxic effect was observed at the dose level of 500 mg/kg.